How many known elements have atoms, in their ground-state, with valence electrons whose quantum numbers are n = 5 and l = 1?a. 36.. b. 37.
c. 6.
d. 8.

c. 6.

Explanation:

Looking at the description given in the question, the elements involved must belong to the p- block of the periodic table and must be in period 5. They also must possess valence electrons in the 5p- orbital.

Now if we look at the p- block of period 5, the following elements satisfy these  requirements; Sr, In, Sn, Sb, Te and I.

Hence there are six of such elements.

the answers would be

the first one and the second one